1. Field of the Invention
The present invention relates to a sealing structure for sealing a region of an article to be sealed (hereinafter, sometimes referred to simply as a seal region) utilizing a fixed form sealing material used for making the article airtight and waterproof, or airtight and moistureproof. More particularly, the present invention relates to a sealing structure for a seal region using an isocyanate group containing reactive polyurethane adhesive in the case where a fixed-form sealing material is applied to seal regions of an air conduct joint, a seam between the tail lamp and chassis of a car, a joint of the cool air conveying duct of a refrigerator, contact surface of the casing and lid of a hard disk driving case, and the like.
2. Description of the Related Art
By the term xe2x80x9cfixed form sealing materialxe2x80x9d is meant a sealing material that is already given a predetermined shape in advance before use. This term is used to distinguish it as a sealing material that has already a fixed form prior to use in contrast to a liquid sealing material such as a liquid type caulking material or a liquid type sealing material that is liquid and will be cured or have a fixed form only after being applied. The fixed form material includes those sealing materials made of rubber or plastic and molded into a predetermined configuration, those made of rubber or plastic and molded into a sheet of plate that is then punched into a predetermined shape.
Upon application of such fixed form sealing materials to the seal region as described above, generally a method is used in which a pressure-sensitive adhesive in the form of a tape with a release paper on each surface, i.e., a so-called double coated tape, is applied to one surface of a fixed form sealing material and the release paper is peeled off so that the sealing material is attached to the seal region through the adhesive layer.
However, the attaching method as described above has various problems in that it involves the trouble of first applying a double coated tape to a fixed form sealing material. Double coated tapes are expensive. Further, costs for attaching are incurred. After use, the release paper becomes a waste material, which must be disposed of and thus causing the problem of disposal thereof. The punching of a sealing material from a plate-like sealing material results in the occurrence of punching loss. Because both the sealing material and double-coated tape are used, it is difficult to separate them for subsequent recycling. As a result, the disposal of waste becomes very difficult. In addition, the total cost is very high.
With a view to solve these problems, it has been proposed to integrally mold a pressure sensitive adhesive together upon producing a sealing material to eliminate the cumbersome procedure of attaching the double coated tape. However, even this method is not free of the problems of disposal of waste release paper and punching loss.
On the other hand, a method of applying a sealing material to the seal region with a solvent type or aqueous type adhesive may be used. However, this method has problems in actual application in that it takes a long time for drying the solvent or water, or the material used has odor. Further, when using aqueous adhesives, there will occur a considerable decrease in waterproofness and moistureproofness after the application of a fixed form sealing material. If the article to be sealed is washed with water after the application of a fixed form sealing material as in the case of hard disk drive (HDD) casing, the bonded portion is vulnerable to water and tends to be peeled off.
To alleviate the aforementioned defects of the adhesive, a hot-melt adhesive may be used in bonding a fixed form sealing material to the seal region. However, the conventional hot-melt adhesive can be coated either to the fixed form sealing material or to the seal region, and in each case the timing in which the fixed form sealing material cab be bonded is extremely limited the adhesive tends to be cooled readily. Where the fixed form sealing material is a foamed material, the situation might be worsened since the bonded surface is uneven or with protrusions and depressions, so that sufficient bonding area cannot be reserved; as a result, the bonding is difficult and tends to cause a problem. This is also the case where the seal region is xe2x80x9cwood materialxe2x80x9d that has likewise many protrusions and depressions so that bonding is difficult to achieve and proper timing for bonding is difficult to be determined.
Even if a hot-melt adhesive is used, the difficulty in determining the proper timing for bonding remains since the conventional hot-melt adhesive or pressure-sensitive adhesive has high viscosity so that it must be coated at a high temperature and the viscosity increases greatly after the coating.
In addition, the conventional hot-melt adhesive has the defect specific thereto that in summer seasons, while parts with the sealing material attached thereto are being stored in a warehouse, the fixed form sealing material bonded could be peeled off.
Further, if a fixed form sealing material is bonded between the casing and lid of a hard disk drive (HDD) casing with a conventional hot-melt adhesive containing a tackifier and a large amount of an oil component in order to prevent a decrease in viscosity, these components generate gases, which contaminate the HDD and cause a trouble.
Under the circumstances, the present invention has been made to solve the aforementioned problems of the conventional sealing structure and an object of the present invention is to provide a sealing structure that can be easily applied and does not use any double coated tape, causes no problem in disposal of wastes, highly waterproof and causing no decrease in waterproofness nor moistureproofness upon washing, generates no gas that could adversely affect the member to be sealed, and is inexpensive.
To achieve the aforementioned object, according to a first embodiment, the present invention provides a sealing structure for sealing a region of an article to be sealed, characterized by comprising a fixed form sealing material bonded to the region with an isocyanate group containing reactive polyurethane hot-melt adhesive.
In a second embodiment, the present invention provides a sealing structure for sealing a region of an article to be sealed, characterized by comprising a sealing member comprising a thin substrate for attachment and a fixed form sealing material bonded to said substrate with an isocyanate group containing reactive polyurethane hot-melt adhesive, said sealing material being airtight and waterproof or airtight and moistureproof, and said region having provided thereon said sealing member.
Here, the reactive polyurethane hot melt adhesive may have a contact angle of 90xc2x0 or more.
The fixed form sealing material may have a contact angle of 90xc2x0 or more.
The fixed form sealing material may comprise at least one material selected from the group consisting of polyurethane foam, polyurethane nonfoam, EPDM foam and EPDM nonfoam.
The region to be sealed may be a region between a box and a lid of a hard disk drive casing.